Direct Time Domain Downtime Assessment For LNG Operations Using Computer Cluster

Time domain simulations are used extensively to assess the availability of offshore offloading operations, providing key input for assessing the economical viability and reliability of offshore LNG projects. Traditionally, wave scatter diagrams, RAOs or “look-up tables” have been used for this, comprising assumptions which may be difficult to justify. For free weathervaning structures, the relevant combinations of wind, sea, swell and current conditions are virtually unlimited. The uncertainties related to the approximated methods, together with the increasing computing capabilities, has led to the development of a novel method for direct time domain calculation of the downtime events for several years of environmental data. The new approach provides much better insight in the downtime events, including occurrences of crossed conditions, beam swells and varying vessel headings. The complete operation, including approach, berthing, tug operations, side-by-side offloading and departure, can be studied with properly calibrated numerical models. Persistency and seasonality can be evaluated in a direct and consistent manner. For demonstration purposes the new method was applied for a generic FSRU offshore Rotterdam port (52N/3E). Actual floating LNG terminals will probably be located in more sheltered areas, but the chosen location has the advantage of being far outside the main coastal traffic routes.